Telephone receiver



A. A. THOMAS .TELEPHONE RECEIVER Filed May 16, 1925 Patented Feb. 9, 1926.;

PATENT OFFICE,

ADOLPH TEIQMAS, NEW YORK, N. Y.

TELEPHONE RECEIVER,

. Application filed Kay 16, 1925. Serial Ho. 80,708.

To all whom it may concern: Be it known that L'Anonrrr A. THOMAS, a citizen of the United States, and a resident of the city of New York, county and State of New York, have invented certain new and useful Improvements in Telephone Receivers, of which the following is a specification.

My invention relates to telephone receivers, and is particularly applicable n the construction of loudspeakers for radio receiving circuits, although not limited to such use.

Broadly stated, the telephone re'ceiyer of my invention comprises a pair of coils for controlling the operation of a movable armature. One or these coils is adapted to be connected in series in a circuit of substantially constant potential, and the other coil is connected in shunt to a variable resistance in series with the first coil. If this resistance is varied in accordance with trans ance and thereby reproduce the transmitted intelligence. 0 a In the preferred embodiment of my invention', the coils are normally arranged in substantially counterbalancing relation to,

the armature, so that normally the armature is held in balanced position. When an acoustic diaphragm is connected to the armature, the normal tlow of current in the circuit produces no strain on the diaphragm through the armature connection.

If my invention is used in a radio receiving circuit, the coils are directly connected in the plate circuit, thereby obviating the use of a transformer. In this case, one coil is in series in the plate circuit, and the other coil is in shunt to the plate-filament path of the tube. Changes in the resistance of this path, as by variations in grid p0 tential, produce current fluctuations in the two coils and cause the magnetic edect of one coil to preponderate over that of the other in relation to the armature. This unbalancing of the coils produces vibration of the armature in accordance with current fluctuations in the plate circuit.

W hen my invention is embodied in aloudspealrer connected in a radio-receiving circuit, I preferably employ automatic means for interrupting the battery circuit through the coils when no current flow across the plate-filament path of the vacuum tube in which the loudspeaker is connected.

To explain the underlying principles of my invention, I have shown diagrammatically several embodiments of my new telephone receiver as applied in a radio receiving circurt, it being understood that this is merely by way of illustration and not as a restriction or limitation. In the accompanying drawing, which forms part of this specification- Fig. 1 represents, in a diagrammatic way, a rormof my invention containing a magnet with bifurcated pole pieces, the series coil and the shunt coil consisting each of two windings arranged on opposite polar bifurcations Fig 2 shows a somewhat simplified constructiongun which only one of the magnet poles is bifurcated to carry the two coils, and in which there is an automatic cut-out for the coils when no current flows across the plate-filament path; and Fig. 3 illustrates a modification employing a three-pole magnet and having a switch for simultaneously controlling the circuits pat the filament battery and the plate batery.

To promote clearness in the drawing, the parts are indicated as simply as possible and no attempt has been made to represent any detalls in correct mechanical or electrical proportion. In all the figures, V represents a suitable vacuum tube havingthe usual three electrodes, P the plate, G the grid, and F the filament. It will be understood that the grid is properly connected in circuit, so that variations in grid potential take'place in accordance with the electric Waves received by the radio set. The battery B is the usual plate battery of proper potential and connected in circuit between the plate and the filament of the tube, as will be clear to all who known anything about radio circuits.

In Fig. 1, there is a permanent magnet indicated as a whole by M. This magnet has a pair of bifurcated pole pieces N and S,

which are preferably made of soft iron furcations and is thus held magnetically roughly the opposing or counter-balancing effect of the windings 1:1 and 8 on the adbalanced, or as nearly so as practical conditions permit. To the armature 6 is connected an acoustic diaphragm D through a link 7. lit will be understood that the diaphragm D is properly supported for vibratory movement.

0n the polar extensions or bifurcations 2 and 8 are mounted windings 8 and 9, respectively. These windings are connected in series with each other by a conductor 10, and are adapted to be connected in series in the circuit of battery B. The windings 8 and 9 constitute in effect a single coil, which I will call the series coil.

On polar bifurcations 1 and 4e are mounted windings 11. and 12, which are connected together in series by a conductor 13. These windings constitute in effect a single coil, which I will name the shunt coil, for a reason which will presently become clear. The free end of winding 12 is connected by a conductor 14 to the negative side of battery B, while the free end of winding 11 is connected by a conductor 15 with the battery line 16.

It will be clear from the foregoing that the coil 89 is connected in series with the variable resistance path P-F of the vacuum tube, and that the coil 1112 is connected in shunt to this resistance path. For this reason I refer to the coil 1112 as the shunt coil.

The windings of series co'il 8-9 produce a magnetic effect which is substantially equal and opposite to the magnetic effect produced by the windings 11 and 12 of the shunt coil. That is to say, when the plate current remains substantially constant, the resultant mag'netioeffect of the coils on the armature 6 is practically zero or neutral. This means that normally the armature is held magnetically balanced, so that the normal strain on the armature is a negligible minimum. The arrows a and b are intended to indicate jacent armature end, and the arrows c d indicate the same normal relation of windings!) and 12 to the other end of the arma- The windings 8 and 9 of the series coil are so calculated with respect to the windlngs 11 and 12 of the shunt coil that normally the magnetic effects of these two coils on the armature practically neutralize or counterbalance each other, as just explained. To facilitate an adjustment of the coils, it may be desirable to insert a manual- 'ly adjustable resistance in series with one of the coils. lln the present instance, T have shown a variable resistance 17 for regulating the current flow through the shunt-coil 1l12.

The operation of the construction shown in Fig. 1 will now be clear to those skilled in the art, and may briefly be described as follows: Normally, when the grid G is not functioning to vary the electronic resistance path P-F of the vacuum tube, the current flowing through the plate battery B is substantially constant. This current flows through the windings 8 and 9 of the series coil, and then divides through two shunt or parallel paths-one shunt including the plate-filament path of the vacuum tube, and the other shunt including the windings 11 and 12 of the shunt coil. The battery current divides through these two shunt paths in inverse proportion to their resistance. As stated before, the series and shunt coils are so calculated that under normal conditions the current flowing through these coils produces magnetic effects which are substantially equal and opposite in their relation to armature 6, so that normally there is no movement of the armature. When the grid potential of the tube V varies, as during broadcast reception, the resistance of the path PF varies accordingly, and this produces corresponding current changes in the circuit of the plate battery. This fluctuating current passes through the series coils 8-9 and a portion of it flows through the shunt coil 11-12. The amount of' current passing through the shunt coil at any 1nstant depends upon the resistance of the path P-F of the tube. Under these current fluctuations in the plate circuit, the normal counterbalancing relation of the coils to the armature is upset, with 'the result that the armature vibrates in accordance with current fluctuations in the circuit. movements of armature 6 are communicated to the acoustic diaphragm D, which thus audibly reproduces the received signals.

In the arrangement shown in Fig. 2, the magnet M has only one bifurcated pole piece N. The armature 6' is pivoted at 18 to the opposite pole of the magnet (in this instance the south pole S), and is operatively connected to a diaphragm D. On one bifurcation of pole piece N is mounted a series coil 19, and on the other bifurcation is mounted a shunt coil 20. Otherwise. what has been said concerning Fig. 1 is fully applicable to Fig. 2 without the necessity of detailed repetition.

In order to prevent the current of battery B from flowing through the coils 19 and 20 The when the filament is not operating,that is,

' to open and close a pair of switch contacts 33. All the switch parts are shown for clearness merely in a diagrammatic way. It is plain that, as long as current flows through conductor 34 across the plate-filament path P-F, the coil 30 is energized and holds the armature 31 in a position to close the contacts 33, thus closing the bat tery circuit through the coils 19 and 20. Now, when. the filament circuit is interrupted no current flows across PF from the plate battery, the coil 30 is de-energized and the armature 31 drops away from the con tacts 33, thereby breaking the circuit through coils 19 and 20. When the" filament F is again placed in operative condition, so that current flows through coil 30 across the PF path, the armature 31 is actuated to close the contacts 33.. This operation of switch H to control the circuit through coils 19 and 20 is entirely auto- 'matic, requiring no attention on the part of the user. The switch H, which can, be made quite small and for a few cents, may be placed in the instrument as a part thereof.

In Fig. 3, we have a magnet M provided with three pole pieces 21, 22 and 23. It is immaterial whether the outside pole pieces are north poles and the center pole piece a south pole, or vice versa. On pole piece 21 is mounted a series coil 24, and on pole piece 22 is arramzed a shunt coil 25. An armature 26 is pivoted on the magnet structure at 27, and is connected to an acoustic diaphragm D The armature 26 is normally heldmagnetically balanced by the magnet. since each end of the armature is attracted by the adjacent pole piece with practically the same force. Coils 24 and 25 are so calculated that normally their magnetic efitect on the armature is equal and opposite. When the grid is functioning to vary the resistance of the path P-F., the counterbalancing relation of the coils .24and 25 is disturbed, as previously explained, and the armature vibrates in accordance with the prepondcrating magnetic eftect of one coil over the other under the current fiuctu ations in the plate circuit.

The modification in Fig. 3 is provided with a switch for simultaneously cont-rolling the circuit. connections of the filament battery and'plate battery. Inthe line 35 of the filament circuit is a spring arm 36 arranged to engage a switcl1"contact 37.

Similarly, a spring arm 38 is connected in the line 39 of the plate circuit to engage a switch contact 40. An insulated plug 41.

supposedly mounted on the front panel of the radio set, controls the contacts 36 and 38. The switch arms 36 and 38, with their associated contacts, and the plug 41, constitute a cut-out switch indicated as a whole by J.

Normally, the switch arms 36 and 38 are open, as shown in Fig. 3. In this position of switch .l. both the filament battery and the plate battery are out of circuit. When the operator pushes in the plug 41, these circuits are simultaneously closed, and the coils 24 and 25 function as above described. When the operator wants to put the radio set out of use, he simply pulls out the switch plug 41, which automatically disconnects the filament battery and the plate battery.

It will be understood that the switches -H and J represent merely illustrative examples of suitable devices for automatically cutting out the controlling coils of the instrument when current ceases to flow across the variance path PF may be any resistance adapted to be varied in accordance with changes in current or voltage in the controlling circuit. lit found necessary or desirable, a condenser of proper capacity may be shunted across the battery lines (Fig. 1, 2 or 3) to absorb any radiofrequency currents that may have strayed into the plate circuit, as will be understood by the radio expert. This condenser should be such as not to interfere with the audio frequency current fluctuations in the plate circuit.

Although it have herein shownand described certain specific constructions and circuit arrangements, it is obvious that the basic principles or my invention may be mechanically carried out in other ways than herein set forth by way of example.

This application is a continuation in part of my pending application Serial Number 724.749, filed July 8, 1924.

What it claim as my invention isz' 1. ln a telephone receiving circuit, a mag net having pole pieces, a vibratory armature operatively associated with said pole pieces, acircuit containing a battery of substantially constant potential, a variable resistance path in series with the battery, means for varying the resistance of said path in accordance with transmitted intelligence, a coil on said magnet in series with the battery, a second coil on said magnet in shunt to said variable resistance path, said coils being so constructed and arranged that noro equal and opposite, whereby current varia-- mally their resultant magnetic effect on the armature is substantially equal and opposite, whereby current variations in the battery circuit due .to variations in said resistance path unbalance the magnetic effects of said coils and cause vibration of said armature in accordance with said current variations, and an acoustic member controlled by said armature.

.2. In a radio receiving circuit,.a magnet having pole pieces, a vibratory armature operatively associated with said pole pieces, a vacuum tubehaving the usual three electrodes, a battery in the plate circuit of'said tube, a coil on said magnet in series with the plate battery, a second coil on said magnet in shunt to the plate-filament path of the tube, said coils being so constructed and arranged that normally their resultant mag netic effect on the armature is substantially tions in the plate circuit due to variations in grid potential unbalance the normally balanced magnetic effects of said coils and cause Vibration of said armature in accordance with said current variations, and an acoustic member controlled by said armature.

3. In a radio receiving circuit containing a vacuum tube with the usual electrodes,

a series coil in the plate circuit of the tube, a second coil in shunt to the plate-filament path of the plate circuit, and a movable magnetic member controlled by the joint action of said coilsin accordance with current variations in the plate circuit, said coils being so constructed and arranged that normally their magnetic effect on said member is practically neutral or balanced.

4:. A telephone receiver for radio receiving circuits, comprising a magnet provided with a pair of coils" which normally balance or neutralize each other in their magnetic effect, one of said coils being adapted to be connected in-series in the plate circuit of a vacuum tube, the other coil being adapted to be connected in shunt to the plate-filament path of the plate circuit, and a movable armature associated with said magnet and controlled by the joint action of said coils.

5., A telephone loudspeaker comprising a magnet provided with a movable armature,

. a pair of coils mounted on said magnet in such relation as practically to neutralize or balance each other normally in their magnetic efiect on said armature, one of said coils being adapted to be connected in series with a source of substantially constant normally balanced potential, the other coil being adapted to be connected in shunt to a variable resistance path in circuit with said source, whereby variations in said resistance path alter the relative proportion of current flowing through said coils and thus upset the magnetic balance of the coils to cause movement of said armature, and a diaphragm operated by said armature.

6. In a telephone receiving circuit, a magnet having pole pieces, one of said pole pieces being bifurcated, ayibratory armature operatively associated with said pole pieces and normally held magnetically alanced between the bifurcations of said pole piece, a circuit containing a battery of substantially constant potential, a variable resistance path in series with the battery, means for varying the resistance of said path in accordance with transmitted intelligence, a coil on one of said bifurcations in series with the battery, a second coil on the other bifurcation in shunt to said variable resistance path, said coils being so constructed and arranged that normally their resultant magnetic effect on the armature is substantially equal and opposite, whereby current variations in the battery circuit due to variations in said resistance path unbalance the normally balanced magnetic effects of said coils and cause vibration of said armature in accordance with said current variations, and an acoustic member controlled by said armature.

7. In a radio receiving circuit, a magnet having pole pieces, one of said pole pieces being bifurcated, a vibrator armature operatively associated with sai pole pieces and normally held magnetically balanced between the bifurcations ofv said pole piece, a vacuum tube having the usual three electrodes, a battery in the plate circuit of said tube, a coil on one of said bifurcations in series with the plate battery, a second coil on the other bifurcation in shunt to the plate-filament path of the tube, said coils being so constructed and arranged that normally their resultant magnetic effect on the armature is substantially equal and opposite, whereby said current variations. in the plate circuit due to variations in grid potential unbalance the normally balanced magnetic effects of said coils and cause vibration of said armature in accordance with said current variations, and an acoustic member controlled bysaid armature.

8. In a telephone instrument, the combination of a vibratory magnetic member, and 'a air of coils operatively associated with said member in such relation that normally their magnetic efiect on said member is practically neutral or balanced, one of said coils being adapted to be connected in series with a source of substantially constant potential, the other coil -being adapted i tube having plate and filament electrodes, a

coil in the plate circuit of to be connected in shunt to a variable resistance path in circuit with said source.

9. In a telephone system, a vacuum tube having late and filament electrodes, a series coil in t 1e platecircuit of the tube, a second coil in shunt to the plate-filament path of the plate circuit, whereby both coils are subject to current variations in said circuit, and a movable magnetic member controlled by said coilsin accordance with current variations in the plate circuit.

10. Ina radio circuit, a vacuum tube having plate and filament electrodes, a series the tube, a second coil in shunt to the plate-filament path of the plate circuit; and a member controlled by said coils in accordance with current variations in the plate circuit. .1 U

11. In an electric amplifying circuit having a path of variable resistance, a coil in said circuit in series with said variable resistance path, a second coil in said circuit in shunt to said path, and a movable member controlled by said coils in accordance with current variations in said circuit due to variations in said resistance path.

12. In a radio receiving circuit, a vacuum series coil in the plate circuit OI the tube, a second coil in shunt to the plate-filament path of the plate circuit, a movable armature controlled by said coils in accordance with current variations in the plate circuit, and an acoustic diaphragm operatively connected with said armature. I

13. In a telephone system, a circuit having a path of variable resistance adapted to be controlled in accordance with transmitted impulses, a pair of coils in said circuit, one of said coils being in series with said variable resistance path and the other coil being in shunt to said path, and an acoustic device controlled by said coils in accordance with current varlations in said circuit. 14. In a telephone system, a vacuum tube having plate and filament electrodes, a series coil'in the plate circuit of the tube, a second coil in shunt to the plate-filament path of the plate circuit, whereby both coils are subject to current variations in said circuit, a movable magnetic member controlled by said coils in accordance with current variae tions in the plate circuit, and means for automatically interrupting the battery circuit through said coils when no current flows controlled by said coils in accordance with current variations in said circuit due to variations in said resistance path, and mechanism for automatically interrupting the circuit through said coils when the circuit through said resistance path is broken.

16. In a radio circuit, a vacuum tube having. plate and filament electrodes, a series coil in the plate circuit of the tube, a second coil in shunt to the plate-filament path of the plate circuit, a member controlled by said coils in accordance withcurrent variations in the plate circuit, and a switch for automatically interrupting the battery cir cuit through'said coils when the filament circuit is broken.

17. In a radio receiving circuit containing a vacuum tube with the usual electrodes, a series coil in the plate circuit of the tube, a second coil in shunt to the plate filament path oi the plate circuit, a movable magnetic member controlled by the joint action of said coils in accordance with current variations in the plate circuit, said coils being so constructed and arranged that normally their magnetic effect on said member ispracticalv ly neutral or balanced, switch contacts in the circuit connections of said second coil, and means governed by the flow of current across said plate-filament path for holding said contacts closed, said means automatically opening said contacts when no current passes across the plate-filament path.

" ADOLPH A. THOMAS. 

